During the course of research and development, production and other technological activities in a variety of different fields, a need arises to handle, transfer and dispense very small volumes of liquid. "Micro volume" liquid handling and dispensing systems, suitable for handling liquid volumes on the order of a microliter, have been developed to satisfy such a need.
Micro volume liquid dispensing systems are categorizable, generally, into one of two groups based on the way in which they dispense their charge of liquid. In a first group of such micro volume delivery systems, a portion of the dispensable liquid, while still in its dispenser, is brought into contact with a receiving body ("the receiver"). Based on a difference in surface tension between liquid in the dispenser and liquid contacting the receiver, the liquid is drawn out of the dispenser and into the receiver. Such systems may be categorized as requiring "touch-off." Exemplary touch-off-based micro volume dispensing devices include capillary tubes, wettable pegs or pins and syringes using "drop touch-off," among others. Dispensing devices included within the first group tend to be mechanically simple and inexpensive. Unfortunately, it may be undesirable or impractical to bring the dispenser close enough to the receiver to effect liquid contact. In particular, in the medical, chemical and biological arts, such close contact may cause undesirable carryover or cross contamination wherein a substance in the receiver is drawn into or onto the dispenser. Moreover, cleaning capillary tubes and syringes, such as may be required between each touch-off due to a change in the dispensed liquid or to avoid cross contamination, can be problematic.
In a second group of micro volume liquid dispensing systems, which may be categorized as "non touch-off," the dispensable liquid is forcibly ejected from the dispenser. Exemplary devices utilizing such an ejection method include piezo or thermally-actuated liquid ejectors as are often used in print heads, solenoid modulators of pressurized liquid flows and micrometering pumps. Such devices avoid the aforementioned drawback associated with touch-off; however, they suffer from other drawbacks. In particular, both piezo and thermally actuated liquid ejectors are limited to use with extremely small volumes of liquid, and typically require very clean and specially-developed fluids. Such restrictions limit the utility of liquid ejectors in chemical, biochemical and related arts. Pumps and flow modulators are usually very expensive, bulky, slow, have limited reliability and are often incompatible with biochemical or chemical reagents, as well.
Moreover, most of the conventional micro volume liquid dispensers mentioned above are not readily adaptable for use in systems requiring multiple dispensing ports. As such, their use is precluded or substantially curtailed in high throughput chemistry and screening applications. Thus, there is a need for a simple and reliable system suitable for transferring small volumes of a variety of liquids and possessing multi-point dispensing capability.